LSHTM Research Online

Tuberculosis control in a South African community with high HIV prevalence: the role of intensified case-finding and antiretroviral therapy

Kranzer, Katharina;
(2012)
Tuberculosis control in a South African community with high HIV prevalence: the role of intensified case-finding and antiretroviral therapy.
PhD (research paper style) thesis, London School of Hygiene & Tropical Medicine.
DOI: 10.17037/PUBS.00682445

Abstract

This thesis investigates active TB case finding and antiretroviral therapy for
tuberculosis control in a setting with high HIV prevalence in Cape Town, South
Africa. Many countries in sub-Saharan Africa have seen a worsening tuberculosis
epidemic since the 1990s. Rising tuberculosis incidence rates have largely been
attributed to high HIV prevalence in this region. Conventional tuberculosis control
efforts focus on passive case finding and high cure rates in smear-positive patients,
achieved through short course chemotherapy. These control strategies are
insufficient in controlling the tuberculosis epidemic where HIV prevalence is high.
Additional control strategies have been proposed, including active tuberculosis
case finding, isoniazid preventive therapy for HIV infected individuals, infection
control and antiretroviral therapy.
The feasibility, uptake, yield, treatment outcomes and costs of population-based
active tuberculosis case finding are investigated in the first part of the thesis. The
second part determines losses along the HIV care pathway, community
antiretroviral coverage and the association between coverage and tuberculosis
risk.
The main finding is that population-based active tuberculosis case finding linked to
a mobile HIV testing service had a high uptake and yield. Treatment outcomes in
patients diagnosed through active case finding were as good as outcomes in
patients diagnosed through passive case finding in primary care clinics in Cape
Town. Costs were USD 1,177 per TB case diagnosed and USD 2,458 per
3
successfully treated TB case, in an incremental costing analysis adopting a health
service provider perspective.
Analysis of the HIV care pathway in a peri-urban impoverished settlement in the
greater area of Cape Town highlighted substantial losses along the pathway
between HIV diagnosis and antiretroviral therapy. These results illustrate the
operational challenges in achieving high treatment coverage. Antiretroviral
coverage in this community increased from 18% in 2004 to 84% in 2009.
Increasing antiretroviral coverage was associated with decreasing tuberculosis
risk among patients receiving antiretroviral therapy, even controlled for timeupdated
CD4 count, suggesting an effect on transmission, not just on individual
risk reduction.
The impact of active tuberculosis case finding and antiretroviral therapy on
tuberculosis incidence on a population level was beyond the scope of this thesis.
Large scale cluster randomized controlled trials are needed to investigate the
effect of these strategies on tuberculosis control. In the meantime researchers
conducting active tuberculosis case finding studies should be encouraged to collect
data on treatment outcomes and costs. In addition further interventions are
needed to increase retention and linkage to care in individuals prior to initiating
antiretroviral therapy.